The present invention provides an improved valve stem seal and more particularly a valve stem seal having a pumping action for oil to lubricate the valve stem in its associated guide.
An internal combustion engine includes a plurality of intake and exhaust valves, each valve comprising a valve head received in a valve seat defining an intake or exhaust passage and an elongated stem reciprocably mounted in a valve guide formed in the cylinder head of the engine. The end of the valve stem remote from the head is engaged by a rocker arm in an overhead valve engine or by a plunger in an L-shaped engine which is cam operated. Oil may be supplied to the upper end of the stem through an oil splash system or by a localized oil supply through the rocker arm to the point of contact with the end of the valve stem so that lubrication is present between the valve stem and its associated guide.
Oil is also present in the upper cylinder area of overhead cam engines due to slow oil draindown at higher engine speeds. This oil floods the upper valve seal area, making umbrella-type seals not functional in overhead cam engines.
In order to reduce oil consumption and provide optimum engine performance, a seal has been provided for the valve stem ranging from the umbrella-type shield utilized to deflect the majority of oil away from the upper end of the valve guide to a seal closely conforming to and engaging the valve guide boss and valve stem to restrain all oil flow to the valve stem save a thin film acting as a lubricant for the stem in the guide. However, many of these metering-type seals were ineffective and either dried out during use so that no oil was metered or, because of wear, allowed an excess of oil to enter the valve guide. The present invention obviates these problems by providing a valve stem seal with a positive pumping action.
The present invention comprehends the provision of a valve stem seal formed of an elastomeric material tending to prevent capillary flow and closely embracing the valve stem and its associated guide boss. The seal is provided with a cylindrical wall encompassing the valve guide boss and an inwardly extending flange at the upper end engaging the valve stem at its inner peripheral internal surface with a pair of annular lobes separated by an annular groove acting to positively pump oil along the valve stem during reciprocation of the valve.
The present invention also comprehends the provision of a valve stem seal having a pair of sealing lobes engaging the valve stem with an annular groove therebetween providing an oil reservoir for the metering action. Also, above the upper sealing lobe, the internal wall of the flange is angled upwardly and outwardly so that capillary action maintains oil flow downwardly to the sealing lobe area, resulting in oil being constantly provided to the sealing lobe area to prevent the seal from drying out during use.
Further objects are to provide a construction of maximum simplicity, efficiency, economy and ease of assembly and operation, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.